In the era of climate change, before developing and establishing mitigation and adaptation measures that counteract urban heat island (UHI) effects ...
Over the past century, many research studies have been conducted in an attempt to define thermal conditions for humans in the outdoor environment and to grade thermal sensation. Consequently, a large ...number of indices have been proposed. The examination of human thermal indices by thermal subjective perception has become recently a methodical issue to confirm the accuracy, applicability and validation of human thermal indices. The aims of this study are: (a) to review studies containing both calculated human thermal conditions and subjective thermal perception in the outdoor environment (b) to identify the most used human thermal indices for evaluating human thermal perception (c) to examine the relation between human thermal comfort range and outdoor thermal environment conditions and (d) to compare between categories of thermal sensation in different climatic zones based on subjective perception and levels of thermal strain.
A comprehensive literature review identified 110 peer-reviewed articles which investigated in-situ thermal conditions versus subjective thermal perception during 2001–2017. It seems that out of 165 human thermal indices that have been developed, only 4 (PET, PMV, UTCI, SET*) are widely in use for outdoor thermal perception studies. Examination of the relation between human thermal comfort range and outdoor thermal environment conditions for selective indices in different climatic zones shows that the range of the thermal comfort or dis-comfort is affected by the outdoor thermal environment. For the PET index, the “neutral” range for hot climates of 24–26°C is agreed by 95% of the studies where for cold climate, the “neutral” range of 15–20°C is agreed by 89% of the studies. For the UTCI, the “no thermal stress” category is common to all climates. The “no stress category” of 16–23°C is agreed by 80% of the case studies, while 100% of the case studies agreed that the range is between 18 and 23°C.
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•More than 165 human thermal indices have developed so far.•Examination of thermal indices by subjective perception became a methodical tool.•PET, PMV, UTCI, indices are widely used in outdoor thermal perception studies.•The majority of the indices are hardly in use.•The perceived values of the comfort zone for PET and UTCI are quite similar.
Reconstruction changes have been assessed using PET.Small green areas have only local effects on thermal comfortable conditions.Single mitigation and adaptation measures can reduce PET by two ...assessment classes.A NW–SE oriented street canyon (H/W ratio>1.5) provides best thermal conditions.
Adaptation and mitigation measures, which could be utilized in urban planning, were quantified in regard to their influence on thermal conditions for humans. The effects of city-planning redesign on thermal human-biometeorological conditions are analysed in an urban quarter in Stuttgart, Germany. Two micro-climate models are applied to receive quantitative information about mitigation and adaptation measures. The Physiologically Equivalent Temperature (PET) was simulated by RayMan and ENVI-met 3.5 to assess thermal human-biometeorological conditions of the current urban environment. The planned residential area and different green space scenarios are analysed and their thermal conditions are compared. In addition, different orientations and aspect ratios in street canyons were analysed. Aim was to find out how heat stress during summer can be minimized and to optimize thermal comfort and solar access for mid-latitude cities during the whole year. PET was found to be around 10°C lower under trees compared to green areas (38°C) and at least 25°C lower than over sealed areas (48°C). This result corresponds to an increase of heat stress of three thermophysiological assessment classes for PET. Thermal stress can be reduced in a street canyon with a northwest-southeast orientation combined with an aspect ratio of at least 1.5. This configuration allows nevertheless solar access during winter and maximizes the frequency of thermal conditions during the whole year.
The aim of this contribution is both to demonstrate and to explore the general assessment pertaining to the effects of atmospheric factors on human health and general wellbeing. While humans are ...aware of such effects, particularly individually, their concrete and synergetic effects with the human physiological system are, comparatively, not well comprehended. In human biometeorological studies and approaches, the aforementioned effects are analyzed in terms of their effect pathways, and the development of single or complex approaches. Recurrently in the existing literature, such approaches are mostly defined and, respectively, targeted as indexes. The evaluation and assessment of similar factors and parameters that present related effects were subsequently put together and quantified. This approach is described as ‘effective complexes’ or components. The most well-known examples are the thermal complex, air pollution complex (which can be divided into the biological (pollen) and anthropogenic (air pollutants) factors), actinic complex, and finally, the recent or rapid weather changes complex. Most of the approaches focus on the negative effects consequential to the established criteria ranging from empirical outputs, to epidemiological studies. As a result, the presented approach does not only include the negative effects or implications on humans. Instead, it also highlights the neutral and positive effects which were acknowledged by the research. The approach deals furthermore with the combined effects of different complexes or components and incorporates different weightings of the factors based on the disclosed effects. In addition, seasonal and exposure factors are deliberated upon to differentiate annual variability factors. Finally, the presented approach builds upon a way in which to cogitate how the complex interactions associated to weather and climate can be quantified in a more appropriate way in the context of human health. The approach aims to be applied for a specific weather forecast enabling the communication and balance between human health factors, and also more encompassing climatic analysis.
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•Urban microscale warning systems consider local conditions and structures.•Composition of heat mitigation factors of different cities differ.•Local heat adaptation’s efficacy may ...decrease due to limited accessibility.•Iso-area analysis evaluates accessibility of protective adaptation factors.
Traditional heat health warning systems focus on severe and extreme heat events at the district or regional level, often overlooking localized risk and protective factors such as healthcare access and urban green spaces. This approach considers less the varying impacts of heat within cities, including the phenomenon of Urban Heat Islands (UHIs) and the diverse needs of different populations. To address these shortcomings, a need for the development of an Urban Heat Health Warning and Information System (UHHWIS) that operates within the framework of Heat Health Action Plans is needed. Such a system integrates national acute heat health warnings with city-specific assessments of UHI effects and other relevant factors. The technical implementation of the UHHWIS involves the calculation and preprocessing of basic factors such as the Normalised Difference Vegetation Index (NDVI), imperviousness, and UHI intensity. Additionally, further factors are assessed, spatially processed, and provided in accordance with Open Geospatial Consortium (OGC) standards. An iso-area analysis is conducted to evaluate the accessibility of protective factors, such as urban green spaces, drinking wells, hospitals, physicians, and pharmacies, based on the city’s road topology. One crucial factor considered in the system is the casting of shadows, which is influenced by both time and location and facilitated through deck.gl. The developed template encompasses all these components into a unified system aimed at protecting vulnerable and risk groups, such as the elderly, through resilient, climate-adapted urban planning. The system provides warnings and information tailored to the urban morphology and prevailing conditions, complemented by a catalogue of potential short- to long-term measures focused on behavioral changes and climate-resilient urban planning strategies. The template can be adapted for use in various European cities, offering valuable insights to decision-makers in city administration for mitigating thermal stress and enhancing resilience against urban heat nowadays and in future.
•Spatial distribution of PET in a city of complex topography.•Transfer from discrete measuring to continuous data.•Application of artificial neural network for mapping.•Mapping of day- and nighttime ...heat stress.•Mapping of the urban heat island.
The gap between point measurements made during a measurement campaign and the required discrete data of human thermal comfort in the form of maps could be overcome by statistical or numerical models. City planners usually demand thermal maps with a resolution below 50m. The required input data for the statistical models were meteorological data at high resolution as well as land use and land cover data including morphological data. Meteorological data were obtained through car traverses on a measuring campaign on hot summer days in July 2014. The chosen statistical approaches of stepwise multiple linear regression and artificial neural network were compared for the case study area Stuttgart, Germany. The Physiologically Equivalent Temperature (PET) was applied to analyse the human thermal conditions taking into account both the meteorological environment and the thermo-physiological parameters including the human energy balance. The polycentric and complex spatial distribution of heat stress and heat load is clearly visible in the created maps. One hot spot is the city centre and its surrounding residential neighbourhood, the other hot spot can be detected in Bad Cannstatt (easterly of the Neckar river valley), including industrial and residential areas. Thereby, the non-linear artificial neural network model delivers better results than the stepwise multiple linear regression model. Advantages of the artificial neural network arise from the possibility to reveal non-linear dependencies and interactions between the variables resulting in a better model fit.
•Single and clusters of trees are quantified on a quantitative manner.•Thermal comfort conditions are strong influenced by solar radiation and wind.•Must appropriate tree for the improvement of ...thermal comfort conditions are Caesalpinia pluviosa.•Reduction of Tmrt can improve thermal comfort conditions about 16°C (PET) during summer condition.
Trees behave in different ways on microclimate due to mainly distinct features of each species and planting strategies especially in the tropics. This paper quantifies the daily and seasonal microclimate behavior of various tree species with different planting design either individual or in clusters. This specific knowledge is an important step in the development of urban design guidelines based on the shading of trees and climate adaptation in urban areas in the tropics. It focuses on human thermal comfort based on the physiologically equivalent temperature (PET) for different species. Twelve species were analyzed: Handroanthus chrysotrichus (Mart. ex A.DC.) Mattos, Jacaranda mimosaefolia D. Don., Syzygium cumini L., Mangifera indica L., Pinus palustris L., Pinus coulteri L.; Lafoensia glyptocarpa L., Caesalpinia pluviosa F., Spathodea campanulata P. Beauv., Tipuana tipu F., Delonix indica F. and Senna siamea L. The results show that shading of trees can influence significantly human thermal comfort expressed by (PET). The species C. pluviosa F. presents the best possibility in terms of PET because it can reduce between 12 and 16°C for individual trees cluster can reduce between 12.5 and 14.5°C. Appropriate vegetation used for shading public and private areas is essential to mitigate heat stress and can create better human thermal comfort especially in cities. The results can be seen as a possibility of improvement of outdoor thermal comfort conditions and as an important step in order to achieve sustainability in cities.
•The study analyses the human thermal comfort of courtyards for Italian climate zones.•It focuses on the annual and seasonal effect of height/width on the PET index.•It emphasizes the seasonal trend ...of thermal comfort.•High height/width has a stabilizing effect on thermal comfort, especially during summer.•The choice of courtyard’s height/width can be linked to specific climatic conditions.
The relationship between urban geometry and microclimate is a relevant topic for both urban planning and urban climatology, as it significantly influences the thermal comfort of individuals. Urban geometry, shaped by building typology, has opposite effects for different seasons, satisfying a demand for compactness in summer, to secure protection from the sun, and openness in winter, to provide solar access.
The study presents a long term numerical analysis of the effect of height/width proportions on the thermal comfort of courtyard typology in Italy throughout the year. According to a detailed version of Köppen-Geiger classification, 6 Italian cities were selected as representative for each climate, excluding Alpine climates: Aosta, Milano, Campobasso, Firenze, Lecce, Catania. The assessment of thermal comfort is based on the Physiologically Equivalent Temperature (PET), calculated using the RayMan model. The input for the model are 30 years data on air temperature, vapour pressure, air velocity and cloud cover, with 3-h resolution, obtained from the meteorological station of each city.
The results of daily median analysis over the year and seasonal frequency analysis indicate that high height/width proportions appear to have a stabilizing effect over thermal comfort. This effect is favourable for both winter and summer season; being more conspicuous in summer than in winter, it benefits more the courtyards located in warm climates.
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